Occurrence of eyespot of cereals in Tunisia and identification of Oculimacula species and mating types

The objectives of this study were to investigate the occurrence of eyespot in commercial spring cereal crops in four climatic areas in Tunisia and characterize the dominant species of Oculimacula responsible for the disease. A total of 294 wheat, barley and oat fields were surveyed for eyespot incidence and severity during four cropping seasons from 2010 to 2014. Eyespot was identified in 63.5% of the fields with an average incidence of 23.1% infected stems. The number of infected fields as well as the incidence and severity of disease increased significantly during the 5 years of the study. A significant difference in the occurrence of eyespot among the climatic regions was noted with the wetter areas having greater disease incidence. The highest incidence of eyespot was recorded in durum wheat and bread wheat fields, whereas barley was significantly less infected. The effect of previous crop on eyespot incidence was not significant. All 70 isolates collected in this study were identified as O. yallundae and among them, 39 were identified as MAT1-2 and 31 as MAT1-1. This study highlights the influence of climatic conditions on the distribution of eyespot in the cereal growing areas of Tunisia as well as the increasing occurrence of the disease. The predominance of O. yallundae is an important consideration in the choice of integrated management strategies for eyespot. The presence of both mating types of O. yallundae in similar proportions suggests that sexual reproduction may be occurring.